Mysterious rock formations discovered on the red planet

The Mars Express mission, led by the European Space Agency, has discovered a windblown plateau and strange rocky mounds near to the Magellan crater on Mars.

Magellan crater and surrounding region on Mars. Image: ESA/ DLR/FU Berlin (G. Neukum).

The Ferdinand Magellan crater, named after the famous Portugese navigator, is about 100 kilometres across, and was the target of the exploration that revealed the strange surface features. They were found in a region located to the southwest of the volcanic region Tharsis on the southern highlands of Mars that covers a surface area of about 21,280 square kilometres – roughly the size of Slovenia.

To the west of this region are light-coloured, irregular protrusions up to two kilometres tall that are likely large fragments or mounds of rock. Their formation could be a result of shattered rock from an impact shockwave or a process called subrosion. Subrosion is explained by volcanic activity in terms of the behaviour of magma beneath the planet’s surface. The rising magma heats frozen ground water which then melts and removes subsurface material as it flows away, resulting in a honeycomb effect in the rock layers. This leads to the subsequent collapse of parts of the rock layers, leaving irregular mounds standing.

Magellan crater and notable features. Box 1 shows light-coloured, irregular protrusions. Box 2 highlights linear features that lead to deep valleys. Box 3 contains a plateau that may have been eroded smooth by dusty winds. Image: ESA/DLR/FU Berlin (G. Neukum)

More unusual features were found in the northern part of this region, too. These features display preferential northwest-southeast orientation and lead to deep, well-defined valleys which are most likely faults. These faults could be linked to a surge in volcanic activity in the Tharsis region causing huge stresses on the planetary crust, or to a possible impact event.

Furthermore, in the centre of the main region is a smooth plateau with barely any signs of stresses or fractures, in direct contrast to its surrounds. The composition of this plateau is unknown, but it is suspected to be the same material as that making up the rocky, fractured mounds in the west of the region. There are also fine trails present, running from southwest to northeast across the plateau. These are thought to be an indication of erosion by fine dust particles, causing a sandblasting effect on the plateau and potentially providing an explanation for its smooth appearance.

Mars Express’s discovery of these unusual surface features is the most recent in a line of successful explorations of the surface, composition and appearance of the red planet.